About 240 kilometers (150 miles) north of Baghdad, in southern Kirkuk, police said four people were killed and 60 wounded by a car bomb followed by a suicide blast that targeted a Shiite mosque. Most of the casualties were Shiite worshipers, police told CNN.

After the blast at the al-Mustafa Mosque, people rushed from the neighborhood to the place of worship to check on their relatives' welfare.

"I told my son not to go to the mosque today, I had a feeling. Thank God he is OK," Um Zainab told CNN as she breathed deeply. "We cannot live like this, we are tired of these ongoing attacks. Oh God, we are tired."

She accused Iraqi politicians of not doing their jobs. "Shame on you if you can't protect our sons and our areas," she said in comments directed to them.

The blast shattered glass in the mosque, outside of which bloodstains were visible.

Abbas Jaber, who was in the al-Mustafa Mosque when the blast erupted, told CNN in a telephone interview that he blames al Qaeda and Baathists for Friday's attacks, but he also expressed frustration with the Iraqi government and security forces.

"If they can't protect us, then they should leave their positions," he said. "Enough is enough. We cannot stand still like this, watching our relatives and friends get killed every day."

The attacks came as thousands of Sunni demonstrators took to the streets for the third consecutive month in the cities of Falluja, Ramadi, Mosul, Baiji, Samarra, Tikrit and Baquba, in the provinces of Anbar, Nineveh, Salaheddin and Diyala. The protesters have been denouncing what they call second-class treatment by the Shiite-led government.

They began in late December, when Sunnis took to the streets in Anbar province, which borders Jordan and Syria, to protest Prime Minister Nuri al-Maliki's order to arrest the bodyguards of Finance Minister Rafaie al-Esawi, a Sunni.

The arrests came hours after President Jalal Talabani, a Kurd who was widely viewed as a stabilizing political force in Iraq, left the country to undergo treatment from a stroke.

Al-Esawi then announced his resignation, effective in March, over the government's failure to meet the demands of Sunni demonstrators to end their marginalization, his spokesman, Aysar Ali, said.

The protesters, who have also demanded the release of detainees they say have been held without charges, called the government corrupt and accused it of unfairly targeting Iraq's Sunni people.

They were angry over an incident that occurred on January 25, also a Friday, when soldiers fired on Sunnis in Falluja who were demanding the Shiite prime minister step down, health officials said.

Iraq's Arab Sunnis and Kurds have accused al-Maliki and his Shiite political party of working to consolidate power by cutting them out of the political process, an allegation that comes as U.S. lawmakers have raised concerns about Iraq strengthening its ties with Shiite-dominated Iran.

Sunnis make up about 20% of Iraq's estimated population of more than 27 million; about 60% to 65% are Shiite.

Since the ouster of Saddam Hussein's Sunni-dominated regime in 2003, Sunnis in Iraq have been largely disaffected. The gulf widened in 2005, when Sunnis boycotted the country's election, opening the way to a government dominated by Shiites.

The sectarian divisions translated into violence in the streets in 2006 and 2007, with fighting that nearly ripped the country apart.

In the past six years, Iraq has grown safer as a robust form of democracy took hold. Sunnis, Shiites, Kurds and others often work together; there has been more political, economic and social stability. Coalition forces that ousted Saddam Hussein's government have departed.